Facile synthesis of hierarchical flower-like Ag/Cu₂O and Au/Cu₂O nanostructures and enhanced catalytic performance in electrochemical reduction of CO₂

Abstract

Novel, hierarchical, flower-like Ag/Cu₂O and Au/Cu₂O nanostructures were successfully fabricated and applied as efficient electrocatalysts for the electrochemical reduction of CO₂. Cu₂O nanospheres with a uniform size of ~180 nm were initially synthesized. Thereafter, Cu₂O was used as a sacrificial template to prepare a series of Ag/Cu₂O composites through galvanic replacement. By varying the Ag/Cu atomic ratio, Ag_0.125/Cu₂O, having a hierarchical, flower-like nanostructure with intersecting Ag nanoflakes encompassing an inner Cu₂O sphere, was prepared. The as-prepared Ag_x/Cu₂O samples presented higher Faradaic efficiencies (FE) for CO and relatively suppressed H₂ evolution than the parent Cu₂O nanospheres due to the combination of Ag with Cu₂O in the former. Notably, the highest CO evolution rate was achieved with Ag_0.125/Cu₂O due to the larger electroactive surface area furnished by the hierarchical structure. The same hierarchical flower-like structure was also obtained for the Au_0.6/Cu₂O composite, where the FE_CO (10%) was even higher than that of Ag_0.125/Cu₂O. Importantly, the results reveal that Ag_0.125/Cu₂O and Au_0.6/Cu₂O both exhibit remarkably improved stability relative to Cu₂O. This study presents a facile method of developing hierarchical metal-oxide composites as efficient and stable electrocatalysts for the electrochemical reduction of CO₂.

Keywords

bimetallic nanostructure / hierarchical metal/oxide nanomaterial / galvanic replacement / electrochemical reduction of CO₂

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